This article addresses written feedback to students' drafts and provides insight into teachers' formative assessment practices. Data are taken from a large cross-disciplinary project on writing and assessment in Norway and comprises a sample of 7th graders' writing processes from 11 schools. Teachers' comments are categorised according to different acts of responding, drawing on theories of language acts. The study also focuses what teachers comment on, and selected examples from students' revisions illustrate how teachers' comments are handled. Findings show that a majority of the teacher comments are directive acts, pointing to specific textual aspects -- and quite seldom in a dialogic way. The directives constitute a continuum illustrating different degrees of teacher control. Constatives are frequent, but do not necessarily contain facilitating explanations. The timing of the response stands out as a critical factor. The discussion underlines a need for writing instruction that invites students to revisions and involves teachers and students in active dialogues on text.